(CBS) JONESBORO, Ark. - An Arkansas medical examiner has ruled that Chavis Carter, the 21-year-old man killed by a gunshot wound to the head while handcuffed in the back of a police car, committed suicide.

Toxicology findings show Carter tested positive for methamphetamine, anti-anxiety medication and other drugs.

According to the report by Deputy Chief Medical Examiner Stephen A. Erickson of the Arkansas State Crime Lab, the bullet that killed Carter entered his skull near his right temple, four inches from the top of his head.

"At the time of discharge, the muzzle of the gun was placed against the right temporal scalp," wrote Erickson.

He went on to state that, "The manner of death is based on both autopsy findings and the investigative conclusions of the Jonesboro Police Department."

The autopsy report released Monday included a drug analysis showing Carter hadn't been drinking the night of the July 28 shooting but his urine and blood indicated methamphetamine use. The report says Carter's blood also tested positive for at least trace amounts of the anti-anxiety medication diazepam and the painkiller oxycodone. His urine test also returned a positive result for marijuana.

Last week, Jonesboro police released video of a police officer approximately the same size as Carter reenacting what may have happened the back of the police car on the night of July 28, when Carter and two other men were pulled over in a traffic stop. Police searched Carter twice but have said they did not find a gun.

The reenactment video shows the officer being cuffed, then sitting in the back seat, retrieving a fake gun from his pants, and bringing the barrel to his right temple. The video also shows still photographs of other officers handcuffed in the backseat of a car, with the fake gun pressed to their temple.

Last Friday, police also released the dashboard video from the police car that pulled over the white pick-up truck Carter was riding in. The video shows Carter being patted down by an officer and then led off-camera and questioned. He was put under arrest when police received information that he had an outstanding drug warrant in Mississippi.

Carter's family and others have questioned the police story, claiming that Carter was not suicidal and questioning whether it would have been physically possible to retrieve a concealed weapon and shoot himself in the head while handcuffed and seated.